The objectives of this study are twofold. The first is to develop and extend the dynamic light scattering technique so that it may be used to study some important biological problems. The second is to use the technique for extensive study of particular systems. Five main areas of research will be pursued: (1) The study of translational, orientational and local relaxation times of biological macromolecules or aggregates in solution. The infinite dilution values of these quantities will be used to obtain information about solution dimensions and flexibility. The dynamics of biomolecules in semi-dilute solutions and also at low ionic strength will also be investigated. (2) The study of resonance enhanced Rayleigh scattering and the possibility of developing a light scattering label technique. (3) The formation morphology and growth of micelles and phospholipid vesicles, (4) electrophoretic light scattering, and (5) the dynamics of small molecules in very viscous media.